One part drinking receptacle, one part delectable, the frosting (theoretically) protects the cookie from becoming soggy and sweetens the coffee a little. You can nibble the cookie while you drink or wait until you've finished. The only thing that could prevent this from being perfect is the cookie itself? Is it tasty? Or is it dry and grainy like so many supermarket packaged cookies?
The next step here seems to be creating a mold shaped like a cup that you can bake your own cookies in - and we have just the cookie for the job.
Better Than a Reusable Coffee Cup from Grist